Media captionMr Brown warned of a "Tory trap" in devolving all income tax to Holyrood

Former Labour Prime Minister Gordon Brown has called for 100,000 Scots to sign a petition urging Westminster to keep promises on devolution.

Mr Brown said there should be "no strings attached" to promises of more powers for Scotland.

And he claimed Conservative plans to devolve income tax were a "trap" which could result in Scottish MPs losing the right to vote on UK income tax.

Alex Salmond described the Labour MP's comments as "astonishing".

The outgoing SNP leader and first minister said Mr Brown was "calling for guarantees on the delivery of something which he himself said during the referendum campaign was already a done deal".

No party leader ever suggested that any further caveats, conditions or even considerations would be introduced then or later into the vowGordon Brown

Mr Brown has proposed allowing the Scottish Parliament to raise a further £2bn in tax revenues and to keep 50% of total VAT income in Scotland - around £4bn.

This was part of a 14-point plan for more powers for Scotland, which also included more controls over job creation, transport, land use, welfare and employment rights.

'Tory trap'

Scotland voted "No" to independence in the referendum of 18 September.

Ahead of the vote, Mr Brown set out a timetable for boosting the Scottish Parliament's powers if voters rejected independence, which was backed by the leaders of the three main pro-Union parties.

Prime Minister David Cameron took Labour by surprise on 19 September when he announced plans to end the anomaly which allows 59 Scottish MPs to vote on England-only legislation, such as health and education.

Downing Street later insisted that "one is not conditional upon the other" but Mr Cameron has been under pressure from Conservative MPs calling for more powers for the rest of the UK if Scotland is to get further devolution.

Mr Brown claimed that "no party leader ever suggested" such conditions in discussions before the referendum.

In a letter to his Constituency Labour Party in Kirkcaldy and Cowdenbeath, he wrote: "The Tory trap that we are in danger of falling into is to devolve all decisions on Scotland's income tax rates away from Westminster and then to deny Scotland representation in votes on budget decisions on income tax rates."

The Conservatives' devolution commission has proposed giving the Scottish Parliament full income tax powers, making it accountable for 40% of the money it spent.

Timetable

Labour, the Conservatives and the Liberal Democrats have all set out their own proposals for further devolution of powers to Scotland but have backed the timetable outlined by Mr Brown, which stipulated:

work to begin on the new legislation on 19 September, the day after the referendum.

a "command paper" to be published by the present UK government setting out all the proposals by end of October.

a white paper to be drawn up by the end of November after a period of consultation setting out the proposed powers

a draft new law to be published for a new Scotland Act in January.

He said it was for Lord Smith of Kelvin, appointed by the government to chair a commission on delivering powers to Scotland, to secure agreement between the parties.

But he added: "At this point we need to understand that whatever the disagreements now over the status of Scottish MPs, the pre-referendum vow signed by each of the pro-devolution parties' leaders contained no ifs, no buts and had no conditional clauses and no strings attached and it was not presented as part of wider proposals yet to be unveiled, but as stand-alone and self-contained.

"To be clear: in my discussions prior to the referendum, no party leader ever suggested that any further caveats, conditions or even considerations would be introduced then or later into the vow."

Mr Brown intends to present his petition to the UK Parliament on 16 October, the same day that he will lead a backbench debate on more powers for Scotland.

'Astonishing development'

"How can Gordon Brown call for people to sign a petition urging Westminster to keep its promises on more powers for Scotland when he himself has already said that is a vow which will be honoured?

"The 'Tory trap' is not the proposals on income tax which Gordon Brown talks about - it is the Tory trap which he and his colleagues are leading people into, in which the issue of more powers for Scotland becomes entangled in a row between factions of the Westminster establishment."

The first minister added: "Many of the people who voted No in the referendum did so in the belief that those new powers would be delivered, and that is what now must happen."

Speaking to the BBC on the weekend after the independence referendum, Scottish Finance Secretary John Swinney, accused the UK parties of "utterly unseemly behaviour".

Mr Swinney, who will take part in the Kelvin commission along with fellow SNP MSP Linda Fabiani, called for "absolutely no backsliding whatsoever".

The Conservatives, Labour, the Liberal Democrats and the Scottish Greens will also be represented.